Data relating to the instantaneous pressure flow relationships in the ascending aorta of man will be obtained with a double-lumen catheter and computed from the pressure gradient. These data will estimate the velocity profile in the great vessels and should provide useful information as to the grade of shearing stress which occurs at the blood-vascular wall interface. In addition, studies of the force frequency response as a measure of contractility will be carried out. Data will be obtained in patients undergoing cardiac catheterization and will involve measurement of the peak rate of change of pressure in the left ventricle with a fidelity catheter. The DPDT will be calculated and the ratio of the controlled DPDT to peak DPDT will be measured as the index of contractility.